The present invention relates to a gas turbine engine and more particularly to a gas turbine engine with a fan driven through a geared counter-rotating low pressure spool.
Gas turbofan engines are subject to ever increasing demands to decrease system fuel burn. There is an inherent mismatch between the speeds at which a turbine develops power efficiently and that of a fan (propulsor) which operates more efficiently at lower speeds.
Counter-rotating systems with a counter-rotating rotor that drives a counter-rotating fan may provide efficient operation as every airfoil is involved in compression or power extraction. This results in a relatively shorter and lighter machine. Disadvantageously, the counter-rotating fan may be relatively complicated and may generate significant acoustic disturbances.